Electric lamp



ELECTRIC LAMP Filed Aug. 14, 1929 2 Sheets-Sheet l ilmieva la ial'encefle/Zal Aug. 16, 1938. c. J. LE BEL ELECTRIC LAMP Filed Aug. 14, 1929 2Sheets-Sheet 2 Patented Aug. 16, 1938 ELECTRIC LAMP Clarence J. Le Bel,Cambridge, Mass., assigner, by

mesne assignments, to Raytheon Manufacturing Company, Newton, Mass., acorporation of Delaware Application August M, i929, Serial No. 3853i?!15 Glaims.. (CL 25u-35) REISSUED Netzteil This invention relates toelectric lamps and particularly to a lamp which will radiate asubstantial portion of its energy in a predetermined portion of thespectrum. The lamp ci this invention is characterized by anextraordinary high instead of neon. In general the gas should have ahigh ionization potential.

When a lamp with such a mixture of gas is energized so that the sastherein becomes ionized, I have discovered that as much as 65% of the 5output of energy lying in the ultra violet portion total radiant energyis emitted in the form oi of the spectrum. ultra violet light having awave length in the A lamp of this character has great utility in case ofmercury of about 2537 angstrom units. many elds. Thus for sterilizingand antiseptic By varying the pressure of the mercury within purposessuch a lamp is very eilcient. Furthennarrow limits this percentage maybe reduced i@ more many chemical reactions, especially obsomewhat as theenergy sees into other wave scure organic reactions such as are involvedin lengths. Apparently some obscure resonance the tanning of leather,treating of foods and the phenomenon is involved in which rare gas pal'-like, are greatly accelerated by ultra violet light. ticles freelyinteract with mercury particles to For purposes such as these it hasbeen found that transfer substantially all energy to the latter 15 onlya comparatively narrow portion of the specand cause it to emit asdescribed. It is possible trum in the ultra violet region is useful andany that some unstable compound of mercury and of the radiant energyoutside of this spectrum is rare gas is formed which emits itscharacteristic therefore wasted. While devices such as merradiation. Theradiation emitted will in general cury arcs in quartz containers aregenerators of be one of the prominent lines of the substance 20substantially powerful ultra violet rays, their having the lowerionization potential, in this radiant energy is nevertheless distributedover a. instance mercury. considerable spectrum in this region with a Byvarying the mercury pressure over the wider resultant loss of eilciency.limits as from 1 to 20 microns, it is possible to An object of thisinvention is to devise a lamp ionize both the gas and the vapor andchange the 25 in which radiant energy in a certain portion of color ofthe resulting light. In fact it is possible the ultra violet spectrum isgenerated in a much to go from the pure color of the gas to the puremore ellicient manner than has previously been color of mercury throughthe combination of the the case. A further object is to devise a lamptwo colors by properly adjusting the mercury which will be simple andcheap and will start vapor pressure. Inthis latter case, however, the 30and operate at reasonably low voltages. lamp does not emit as great aportion of its I have discovered that a metal vapor such as energy inthe narrow region of the ultra violet mercury and an inert gas such asargon or neon spectrum 8S iS true When vthe mercury pressure at certainpressures when carrying a discharge, is maintained within smallerlimits.

exhibit a remarkable phenomenon. Under oper- Referring t0 the drawings,Figure 1 ShOWS 8. 35 ating conditions the pressure of either one ofPreferred embodiment 0f lump 0f Substantially the rare gases may bebetween 1 and 8 mm. while two thirds full size and a circuit forenergizing the pressure of the mercury must be between 1 said lamp. and8 microns. The pressure of the rare gas is Figures 2 and 3 aremOdCutiOuS not very critical and may be varied over sub- Flgure4 showsan induction lamp drawn to full 40 stantially wide limits. It is,however, necessary Ze. to maintain the mercury pressure within criticalReferring to Figure 1, the lamp consists ofa limits. This may be done byeither having the container having a substantially uniformcylinnecessary amount of cooling surface in the tube drical p0rt0n lWith IOunded Spherical DOIOIIS 2 4; or by artificially cooling the tubeso that the deat each end. Most of the light of this lamp is 45 siredpressure is maintained. Apparently it is emitted within the spaceenclosed by portion I immaterial in what manner the gaseous disof thecontainer. Inorder to effectively transmit charge is effected. Thus thedischarge through this ultra violet radiant energy, this 110111011 thegas may beeffected by one or more thermionic may be made 0f quartz 01 aSpecial glass Which cathodes, one or more cold cathodes in the usualreadily transmits such radiations. Portions 2 50 manner or may beeiected by inducing high may be made of ordinary glass if desired inorder frequency alternating currents in the gas. to reduce the cost ofthe lamp. The rounded Sodium or other easily vaporizable metals mayportions 2 of the lamp terminate in end portions also be used instead ofmercury while a com- 3 having reentrant portions 4 terminating inparatively inert gas like nitrogen may be presses 5. 55

Sealed within these presses are a plurality of wires some of which areboth supporting wires and leads while others are merely supportingwires. In order to maintain the assembly, insulating members l havingsuitably spaced apertures through which the various leads and supportingwires pass, are disposed beyond the press. Supported by insulators 8 andwires 1 are two hollow cathodes.

While any type of cathode may be used, I prefer to use a thermioniccathode in order to reduce the starting and running potential. A hollowcathode ot this type is very efficient and has a long life and is notsubject to the destructive bombardment usually present in gas lledtubes. 'I'hese hollow cathodes comprise outer metal members l having acylindrical shape and end walls 9 with a central aperture therethrough.Within members t are cylindrical members I0 supported by wires II and I2respectively. Inner members I0 are cylindrical in shape and at theirends carry smaller cylindrical throat members I3 giving access to theinside of members III. Within cylindrical members III are smallerhousings M welded or otherwise fastened to the inner surface of membersI0. Within these housings are filament heaters Il grounded to thehousing and supported by wires I6 and I1. The inner surface of member lobetween the throat n and the housing Il is preferably coated with suit-'able chemicals such as the oxide of alkaline earth metals in order topromote electron emission therefrom. Upon the energization of heaters I6electron emission takes place from the inside surfaces of members III.During the operation of the tube large quantities of ions are generatedin both cathodes and effectively neutralize the electronic space charge.This has a tendency to reduce the cathode drop and greatly increaseelectron emission therefrom. The lamp is provided with two cathodes,both of which act alternately as anodes when energized by alternatingcurrent.

In order to start a lamp of this character, it is necessary to heateither one or both of the cathodes to cause electron emission. Becauseof the lack of ionization throughout the gas space in the lamp acomparatively high potential in the neighborhood of '100 or 800 voltswill be necessary to start a discharge through the tube. As soon as thedischarge has started, however, the running potential drops to aboutvolts.

In order to reduce the starting potential and thus eliminate thenecessity for complicated apparatus to furnish the high startingpotential, I have devised auxiliary ionizing means. These means consistof wires 20 projecting beyond the cathodes and into the space surroundedby portion I of the container. By impressing between 150 and 200 voltsacross the ionizing wires a sufcient amount of ionization in the gastakes place to enable the tube to have a discharge therethrough.

It is evident that once a discharge has been initiated further dischargebetween wires 20 is not only unnecessary but may indeed be undesirable.In order to eliminate such a discharge after the tube has been started Ipreferably have the entire lamp energized by the transformer shown. Dueto the reaction of various magnetic fluxes the main discharge throughthe lamp operates to cut down the ionizing discharge to a negligiblevalue.

Transformer B0 is energized by a primary coil BI supplied by line wires52 from any suitable source oi' alternating current. Mounted on the sameleg of the core of the primary is a secondary l2 which energizes one ofthe heaters I5 through leads 2| and 2l. Another secondary 53 similar toI2 and mounted on the same leg energizes the other heater Il throughleads 4I and 40. Ionizing wires 2l are energized through leads 30 and l0by a secondary Il on leg ll of the transformer core. Another coil 8B onthe same leg 59 as secondary ll is connected by leads B6 and 51 acrossthe two cathodes of the lamp. Coil IIS opposes Il with the result thatas soon as the main discharge through the lamp is initiated the currentflowing through coil il increases the reluctance of leg M of thetransformer core to such an extent as to drive the magnetic flux throughthe center leg SII and airgap BI. Before the main discharge is initiatedthrough the lamp, the reluetance of leg 50 is so low compared to leg 60that substantially all the flux goes through the former leg. In this wayit is evident that substantial discharge between wires 20 is suppressedupon the lamp coming into normal operation.

The lamp shown in Figure 2 is a modification of Figure 1 in which onlyone cathode is provided and in which the ionizing wires are broken upinto suitable lengths. Portion I of the container of Figure 2 ispreferably the same as Figure 1. The end of the lamp containing thecathode is substantially the same as that shown in Figure 1 with theexception that two ionizing wires 10 and 1I are sealed in press 5 toleads 12 and 13.

If ionizing wires 10 and 1I are too long it has been found that there isa tendency for the discharge to go along these wires, thus reducing theintensity of the gaseous discharge and possibly damaging the ionizingwires. In order to eliminate this I have provided a plurality ofdistinct ionizing wires connected through resistance to each other toprevent any substantial dis charge between the wires. Ionizing wires 14and 1l are suitably supported by wires 16 and 11 sealed in the lamp.Additional ionizing wires 1B and 1il are similarly supported by wires 80and Il. Ionizing wires 1U and 18 are connected through suitableresistances BI and 82 to lead 12.

Ionizing wires 14 and 19 are connected through similar resistances tolead 2I of the cathode. I onizer wire 1I) is connected through aresistance 83 to cathode lead 2|. The values of reslstances 8l, 82 and83 are preferably so chosen as to prevent any substantial currentflowing between the opposing ionizer wires. In this way substantialdischarge between them is prevented.

At the other end of the lamp an anode 85 of any suitable material suchas carbon or the like is supported by wires sealed in press 5. The lampis energized by line wires BB and 81 carrying either direct oralternating current. It is evident that if the current is alternatingthe lamp will rectify while in operation. The anode and cathode areconnected to supply wires B6 and B1 through leads B8, resistance B9 andlead 2|. Resistance 88 is of such a value as to keep the current throughthe lamp at a safe value. In order to energize the heater, lead I6 fromthe heater is connected through a suitable resistance 9U to line wire81. Across lines 86 and 81 is disposed a switch 90 and an inductance 9i.Lead 12 from ionizing wire 1I is connected between the inner point ofthe inductance 9| and switch 90. As soon as the cathode has beenenergized, switch 90 is closed but a short time and then suddenlyopened. The resulting high voltage surge across 75 amena? inductance 9|is transmitted through lead I2 to ionizing wires 1|, 15 and 18 acrossthe gas space to ionizing wires 10, 14 and 19 through lead 13,resistance 83, cathode lead to inner cathode member i0 then through theheating filament, through lead I6 resistance 90 to the other side ofinductance 9|.

The tube of Figure 3 is somewhat similar to Figure 2 in that only onecathode is provided. This may consist of two members |00 of porcelain orthe like having a metal shell around them being suitably treated forelectron emission. Through these members pass heating laments supportedby leads |0|. Leads |02 and cathode lead |03 are sealed in press 5 andact to support the entire cathode. Two ionizing wires |00 and |05 aresuitably supported by wires |06 and |01 sealed in tube The connectionsbetween the anode and cathode and ionizing wires may be similar to thatshown in Figure 2.

In Figure 4 is shown in true form, at substantially full size, anelectrodeless induction lamp comprising a tubular portion and bulb ||2.Either or both may be made of material transparent to the ultra violetrays generated. A coil ||3 energized by a suitable source of highfrequency such as an oscillator encircles bulb ||3 and energizes thelamp.

After the tubes of Figures 1 to 4 inclusive have thus been constructedthey are treated in the customary manner to remove all occluded gasesand exhausted to a high vacuum. A small drop of -mercury vapor indicatedby M may be introduced within the container. In addition, a quantity ofargon or neon may be introduced so that at the operating temperature ofthe tube, the pressure will preferably be within the limits previouslyspecied. When the tube is first started much of the discharge is carriedby the rare gas. The discharge, however, warms the mercury so that itspressure becomes suiiicient for it to partake of the discharge. Within avery short space of time the lamp begins to function as a generator ofultra violet rays.

For example, in a lamp of which the one shown in Figure 1 is drawn toscale and containing neon at about 4 mm. and mercury at about 2 microns,a discharge of two amperes resulted in a very powerful emission of ultraviolet in a region of the spectrum below 2900 angstrom units. A majorportion of this energy was concentrated in the 2537 line. During theoperation of this lamp the current and pressure within the lamp could beadjusted so that practically the greatest portion of the energy wasconcentrated in the 2537 line.

I claim:

1. .An ultra. violet lamp comprising an envelope, containing mercuryvapor at a pressure of between 1 and 8 microns during the normaloperation of the lamp, and an inert gas at a pressure of the order ofbetween 1 and 8 mm. and

`means for producing an electrical discharge in said gaseous filling.

2. A gaseous conduction device including a sealed container containingan ionizable atmosphere, electrodes within said container, a pluralityof auxiliary electrodes within said container extending into the regionbetween said iirstnamed electrodes, means for initiating a dischargebetween said auxiliary electrodes for assisting in the starting of thedischarge between said first-named electrodes, and means responsive tothe current iiowing between said first-named electrodes for suppressingthe discharge between said auxiliary electrodes when said currentreaches its normal operating value.

3. A gaseous conduction device comprising an elongated tubularcontainer, a thermionic cathode sealed in one end of said container,another electrode adapted to function as an anode sealed at the otherend of said container, a gaseous iilling in said container, the pressureof said gas being lower than that at which a discharge will startbetween said cathode and anode upon the application of the operatingvoltage across said cathode and anode, a plurality of auxiliaryelectrodes in said container extending into the region between thecathode and anode, said auxiliary electrodes being spaced apart, thespacing between said auxiliary electrodes being suiliciently small tocause anv ionizing discharge to occur in the gas between said auxiliaryelectrodes when a voltage of the order of the operating voltage appliedto the tube is applied across said auxiliary electrodes, and means forimpressing such voltage across said auxiliary electrodes whereby such 4an ionizing discharge may be produced to cause a main discharge to startbetween said cathode and anode.

4. A gaseous conduction device comprising an elongated tubularcontainer, two thermionic cathodes sealed in opposite ends of saidcontainer, a gaseous lling in said container, the pressure of said gasbeing lower than that at which a discharge will start between saidelectrodes upon the application of the operating voltage across saidelectrodes, a plurality oi auxiliary electrodes in said containerextending into the region between the first-mentioned electrodes, thesaid auxiliary electrodes being spaced apart, the spacing between saidauxiliary electrodes being sufliciently small to cause an ionizingdischarge to occur in the gas between said auxiliary electrodes when avoltage of the order of the operating voltage applied to the tube isapplied across said auxiliary electrodes, and means for impressing suchvoltage across said auxiliary electrodes whereby such an ionizingdischarge may be produced to cause a main' discharge to startbetween-said first-mentioned electrodes.

5. A gaseous conduction device comprising an Velongated tubularcontainer, a thermionic cathode sealed in one end of said container,another electrode adapted to function as an anode sealed at the otherend of said container, a gaseous filling in said container, the pressureof said gas being lower than that at which a discharge will startbetween said cathode and anode upon the application of the operatingvoltage across said cathode and anode, and a plurality of pairs ofauxiliary electrodes, spaced apart within said tubular container, saiddischarge path passing between each of said pairs 4of auxiliaryelectrodes, one electrode of each of said pairs being connected to oneelectrode of each of the other of said pairs through a resistance, theother electrode of each of said pairs being connected to the otherelectrode of each of said pairs through a resistance, the spacingbetween the electrodes of each of said pairs of auxiliary electrodesbeing sufficiently small to cause an ionizing discharge to occur in thegas between said auxiliary electrodes when a voltage of the order of theoperating voltage applied to the tube is applied across said auxiliaryelectrodes.

6. An electric discharge lamp device comprising a container, a gaseousatmosphere therein comprising mercury vapor and a rare gas, and meansfor producing a gaseous electric discharge in said atmosphere, thepressure of the mercury vapor being between one and eight microns andthe pressure of the rare gas being between one and eight millimetersduring the operation of the device.

7. The method ot operating a gaseousconduction lamp comprising acontainer with a gaseous filling of mercury vapor, and an inert gashaving a pressure of the order of between one and eight millimeters, andmeans for producing a gaseous electric discharge therein which consistsin en ergizing said lamp and operating the same while maintaining thevapor pressure of said mercury vapor between one and eight microns.

8. The method of operating a gaseous conduction lamp comprising acontainer, a gaseous illi- `ing in said container, said gaseous iillingcomprising mercury vapor and an inert gas, and means for producing anelectrical discharge through said gaseous filling which consists invarying the pressure oi! the mercury vapor between one and -twentymicrons, whereby the color emitted by said lamp is varied, the pressureof said inert gas being greater than the pressure o! the mercury vVEDO?.

9. A gaseous conduction device including a sealed container containingan ionizable atmosphere, electrodes within said container, a pluralityof auxiliary electrodes within said container ex'- tending into theregion between said first-named electrodes, means for initiating adischarge between said auxiliary electrodes for assisting in thestarting of the discharge between said ilrst named electrodes, saidmeans comprising a trans- Y former having a primary winding and asecondary winding connected to said auxiliary electrodes, and anadditional coil on said transformer energized in response to the currentflowing between said first-named electrodes, said additional coilopposing said secondary coil, whereby the voltage generated in saidsecondary coil is reduced to a negligible value when the dischargestarts between said ilrst-named electrodes.

10. A gaseous conduction device comprising an elongated tubularcontainer, a thermionic cathode sealed in one end of said container,another electrode adapted to function as an anode sealed at the otherend of said container, a gaseous illling in said container, the pressureof said gas being lower than that at which a discharge will startbetween said cathode and anode upon the application oi' the operatingvoltage across said cathode and anode, a plurality of auxiliaryelectrodes in said container extending into the region between thecathode and anode, the spacing between said auxiliary electrodes beingsuiiiciently small to cause an ionizing discharge to occur in. the gasbetween said auxiliary electrodes whenV a voltage oi' the order of theoperating voltage applied to the tube is applied across said auxiliaryelectrodes, whereby an ionizing discharge may be produced to cause a.main discharge to start between said cathode and anode, a circuit forirnpressing a starting voltage to the auxiliary electrodes. and anothercircuit for impressing an operating voltage between the main electrodes,said two circuits being electrically insulated from each other.

11. An electrical discharge lamp comprising a container, a gaseousatmosphere therein, and means i'or producing an electrical dischargethrough said gaseous atmosphere, said gaseous atmosphere comprisingmercury and an inert gas. the pressure of the mercury vapor duringoperation being below eight microns but sutnclently high to becomeionized during operation and to emit radiations therefrom, the pressureo! the inert gas being at a substantially higher order of magnitudesufilcient to permit an ionizing discharge to be initiated therein.

l2. An electrical discharge lamp comprising a container, a gaseousatmosphere therein, and means for producing an electrical dischargethrough said gaseous atmosphere, said gaseous atmosphere comprisingmercury and an inert gas, the pressure of the mercury vapor duringoperation being below eight microns butsuiliciently high to producesubstantially a maximum oi radiation eillciency, the pressure oi theinert -gas being at container, a gaseous atmosphere therein, and

means for producing anA electrical discharge throughsaid gaseousatmosphere, said gaseous atmosphere comprising a metallic vapor and aninert gas, the pressure of the metallic vapor during operation beingbelow eight microns in the path of the discharge but sufficiently highin the path of the discharge to become ionized during operation and toemit radiations therefrom, the pressure of the inert gas being at asubstantially higher order oi.' magnitude sufiicient to permit anionizing discharge to be initiated therein.

14. An electrical discharge lamp comprising a container, a gaseousatmosphere therein, and means for producing an electrical dischargethrough said gaseous atmosphere, said gaseous atmosphere comprisingsodium vapor and an inert gas, the pressure oi' the sodium vapor duringoperation being below eight microns in the path of the discharge butsuiiiciently high in the path of the discharge to become ionized duringoperation and to emit radiations therefrom, the pressure o! the inertgas being at a substantially higher order oi magnitude sui'iicient topermit an ionizing discharge to be initiated therein.

l5. An electrical discharge lamp comprising a container, a gaseousatmosphere therein, and means i'or producing an electrical dischargethrough said gaseous atmosphere, said gaseous atmosphere comprisingsodium vapor and an inert gas, the pressure of the sodium vapor duringoperation being below eight microns in the path of the discharge butsumciently high to produce substantially a maximum oi radiationeiilclency, the pressure of the inert gas being at a substantiallyhigher order of magnitude sufficient to permit an ionizing discharge tobe initiated therein.

CLARENCE J. LE BEL.

